package com.cnepay.android.swiper.widget;

import android.content.Context;
import android.graphics.Rect;
import android.support.v4.view.NestedScrollingChild;
import android.support.v4.view.NestedScrollingChildHelper;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.view.animation.TranslateAnimation;
import android.widget.ScrollView;

/**
 * 弹性ScrollView
 * 默认支持下拉弹回和上拉弹回
 * <p>
 * Modification  History:
 * Date         	Author        		Version        	Description
 * -----------------------------------------------------------------------------------
 * Aug 30, 2016     millerJK          1.0                  1.0
 * April 3,2017     millerJK          2.0                  implement NestScrollChild
 */
public class ReboundScrollView extends ScrollView implements NestedScrollingChild {

    private static final String TAG = "ReboundScrollView";

    // 当滑动的距离最小到10，才认为是上下滑动
    private static final float MINI_DISTANCE = 10.0f;

    //移动因子, 是一个百分比, 比如手指移动了100px, 那么View就只移动50px
    //目的是达到一个延迟的效果
    private static final float MOVE_FACTOR = 0.5f;

    //松开手指后, 界面回到正常位置需要的动画时间
    private static final int ANIM_TIME = 100;

    //ScrollView的子View， 也是ScrollView的唯一一个子View
    private View contentView;

    //手指按下时的Y值, 用于在移动时计算移动距离
    //如果按下时不能上拉和下拉， 会在手指移动时更新为当前手指的Y值
    private float startY;

    //用于记录正常的布局位置
    private Rect originalRect = new Rect();

    //手指按下时记录是否可以继续下拉
    private boolean canPullDown = false;

    //手指按下时记录是否可以继续上拉
    private boolean canPullUp = false;

    //在手指滑动的过程中记录是否移动了布局
    private boolean isMoved = false;

    boolean forbidUp;

    boolean forbidDown;

    private NestedScrollingChildHelper mChildHelper;

    public ReboundScrollView(Context context) {
        super(context);
    }

    public ReboundScrollView(Context context, AttributeSet attrs) {
        super(context, attrs);
        mChildHelper = new NestedScrollingChildHelper(this);
        setNestedScrollingEnabled(true);
    }


    @Override
    protected void onFinishInflate() {
        super.onFinishInflate();
        if (getChildCount() > 0) {
            contentView = getChildAt(0);
        }
    }

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
        super.onLayout(changed, l, t, r, b);

        if (contentView == null) return;

        originalRect.set(contentView.getLeft(), contentView.getTop(), contentView
                .getRight(), contentView.getBottom());
    }

    /**
     * 在触摸事件中, 处理上拉和下拉的逻辑
     */
    @Override
    public boolean dispatchTouchEvent(MotionEvent ev) {

        if (contentView == null) {
            return super.dispatchTouchEvent(ev);
        }

        int action = ev.getAction();

        switch (action) {
            case MotionEvent.ACTION_DOWN:
//                Log.e(TAG, "ReboundScrollView       dispatchTouchEvent: ACTION_DOWN");
                //判断是否可以上拉和下拉
                canPullDown = isCanPullDown();
                canPullUp = isCanPullUp();
                //记录按下时的Y值
                startY = ev.getY();
                break;

            case MotionEvent.ACTION_MOVE:
//                Log.e(TAG, "ReboundScrollView       dispatchTouchEvent: ACTION_MOVE");
                //在移动的过程中， 既没有滚动到可以上拉的程度， 也没有滚动到可以下拉的程度
                if (!canPullDown && !canPullUp) {
                    startY = ev.getY();
                    canPullDown = isCanPullDown();
                    canPullUp = isCanPullUp();
                    break;
                }

                //计算手指移动的距离
                float nowY = ev.getY();
                //纪录下滑动时Y,当滑动的距离小于MINI_DISTANCE 的时候则不认为是滑动
                if (Math.abs(nowY - startY) < MINI_DISTANCE)
                    break;

                int deltaY = (int) (nowY - startY);
                if (forbidUp) {
                    if (deltaY < 0)
                        break;
                }

                if (forbidDown) {
                    if (deltaY > 0)
                        break;
                }

                boolean shouldMove = isSingleSliping(false, deltaY);

                if (shouldMove) {
                    //计算偏移量
                    int offset = (int) (deltaY * MOVE_FACTOR);

                    //随着手指的移动而移动布局
                    contentView.layout(originalRect.left, originalRect.top + offset,
                            originalRect.right, originalRect.bottom + offset);

                    isMoved = true;  //记录移动了布局
                }
                break;

            case MotionEvent.ACTION_UP:

                if (!isMoved) break;  //如果没有移动布局则跳过执行

                // 开启动画
                TranslateAnimation anim = new TranslateAnimation(0, 0, contentView.getTop(), originalRect.top);
                anim.setDuration(ANIM_TIME);
                contentView.startAnimation(anim);

                // 设置回到正常的布局位置
                contentView.layout(originalRect.left, originalRect.top, originalRect.right, originalRect.bottom);


                //将标志位设回false
                canPullDown = false;
                canPullUp = false;
                isMoved = false;

                break;

            default:
                break;
        }

        return super.dispatchTouchEvent(ev);
    }

    /**
     * 是否可以向下拉
     * ScrollView 是否在顶部
     */
    private boolean isCanPullDown() {

        return getScrollY() == 0 && forbidDown;

    }


    /**
     * 是否可以向上滑动
     * ScrollView 是否在底部
     * <p/>
     */
    private boolean isCanPullUp() {
        return (contentView.getHeight() <= getHeight()
                || contentView.getHeight() == getHeight() + getScrollY()) && forbidUp;

    }

    /**
     * 设置是否单向滑动
     *
     * @param isSingleSliping false  手势向上拖动，子View随着拖动而向上，之后不放开点击，在向下滑动使ScroView中的子View可以向下拖动。
     *                        true 子View随着手势可以任意方向反复拖动
     * @param distance        isSingleSliping 为true 的情况下才有效
     * @return 是否应该移动布局 true 应该 false 不滑动布局
     */
    private boolean isSingleSliping(boolean isSingleSliping, int distance) {

        if (!isSingleSliping)
            return canPullDown || canPullUp;
        else
            return (canPullDown && distance > 0)    //可以下拉， 并且手指向下移动
                    || (canPullUp && distance < 0)    //可以上拉， 并且手指向上移动
                    || (canPullUp && canPullDown); //既可以上拉也可以下拉（这种情况出现在ScrollView包裹的控件比ScrollView还小）

    }


    /**
     * forbid pull up
     *
     * @param forbidUp true forbid otherwise false
     */
    public void forbidUpRebound(boolean forbidUp) {
        this.forbidUp = forbidUp;
    }

    /**
     * forbid pull down
     *
     * @param forbidDown true forbid down other false
     */
    public void forbidDownRebound(boolean forbidDown) {
        this.forbidDown = forbidDown;
    }

    @Override
    public boolean onTouchEvent(MotionEvent ev) {
        switch (ev.getAction()) {
            case MotionEvent.ACTION_DOWN:
                break;
            case MotionEvent.ACTION_MOVE:
                break;
        }
        return super.onTouchEvent(ev);
    }

    @Override
    public void setNestedScrollingEnabled(boolean enabled) {
        mChildHelper.setNestedScrollingEnabled(enabled);
    }

    @Override
    public boolean isNestedScrollingEnabled() {
        return mChildHelper.isNestedScrollingEnabled();
    }

    @Override
    public boolean startNestedScroll(int axes) {
        return mChildHelper.startNestedScroll(axes);
    }

    @Override
    public void stopNestedScroll() {
        mChildHelper.stopNestedScroll();
    }

    @Override
    public boolean hasNestedScrollingParent() {
        return mChildHelper.hasNestedScrollingParent();
    }

    @Override
    public boolean dispatchNestedPreScroll(int dx, int dy, int[] consumed, int[] offsetInWindow) {
        return mChildHelper.dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow);
    }

    @Override
    public boolean dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed, int[] offsetInWindow) {
        return mChildHelper.dispatchNestedScroll(dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed, offsetInWindow);
    }

    @Override
    public boolean dispatchNestedPreFling(float velocityX, float velocityY) {
        return mChildHelper.dispatchNestedPreFling(velocityX, velocityY);
    }

    @Override
    public boolean dispatchNestedFling(float velocityX, float velocityY, boolean consumed) {
        return mChildHelper.dispatchNestedFling(velocityX, velocityY, consumed);
    }


}

